New Publications are available for Mathematical analysis
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New Publications are available now online for this publication.
Please follow the links to view the publication.Optimal sizing of hybrid energy resources for electrifying distant rural areas of Iran
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0867
Mathematical models are presented for PVs, wind turbines, battery storages and diesel generators for optimal in a hybrid isolated system. The optimization model is formulated and a case study is run in a rural nonelectrified area of Iran. (4 pages)The role of fast charging stations for electric vehicles in the integration and optimization of distribution grid with renewable energy sources
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0815
In the next 20 years the number of electric vehicles (EV) will exponentially increase. That will be mostly due to governments and car manufacturers which are coordinating the effort to reduce urban pollution and greenhouse gas emission. The energy required for charging EV usually recovering in private parking places for many hours, will be mainly provided through smart charging boxes (“wall box”) managed by the (smart) grid control system of the LV network. In all other cases, EVs will be charged in fast charging stations or battery swap stations connected to the MV network. Such charging stations require high power during the day, especially when the network could be overloaded, hence there is the need to model the impact on the grid. This paper investigates the possibility to use storages to shave peak power demand due to FC stations and the possibility to use these storages to provide additional network services, included the optimization of intermittent-not-programmable energy sources, such as renewable energy. (4 pages)Comparison of planning alternatives for active distribution networks
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0895
A key element on the development of the future active distribution networks is to provide the network with storage devices, in order to compensate possible negative effects brought by a large integration of unpredictable generation. Software tools to aid Distributors to correctly assess the effectiveness of the use of storage as an alternative to traditional planning solutions (e.g. upgrading of the distribution lines) can be useful to planner engineers. The tool developed by the authors assists the DSO in defining the best integration strategies of distributed storage systems in distribution networks and in assessing their potential as an option for a more efficient operation and expansion of future electricity distribution networks. Examples derived by a representative distribution network are presented. (4 pages)Enhanced protection for inverter dominated microgrid using transient fault information
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0081
Protection of an inverter dominated microgrid is always a great challenge, as inverters are well known for their insufficient contribution to the fault current, undermining the accuracy and viability of traditional overcurrent protection schemes. Based on the wide review of solutions developed in the past, this paper proposes a novel protection strategy, with the main protection method based on the time and polarity features of initial current travelling waves using mathematical morphology (MM) technology and backup protection strategy based on the rate of change of current. Simulation tests in PSCAD/EMTDC considering different fault resistances, fault positions and fault inception angles prove this protection approach to be sensitive and reliable. (5 pages)Three-phase photovoltaic inverter small-signal modelling and model verification
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0351
The number of power electronic converters is increasing in the grid due to favourable political climates regarding renewable energy resources. Grid-parallel inverters have been shown to suffer from reliability problems that may not be solved with pure time domain analysis. Therefore, it is important to analyse the dynamics of these converters also in the frequency domain. This paper reviews small-signal modelling method of three-phase converters and proposes a measurement setup utilizing digital signal processing, which can be used to verify the small-signal model. Experimental measurements from a three-phase photovoltaic inverter will be presented. (6 pages)Predictive PID controller for DC-DC converters using an adaptive prediction error filter
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0213
This paper presents a predictive PID controller for DC-DC converters using an adaptive prediction error filter (PEF) in the controller feedback loop. The concept of using an adaptive PEF is clearly described, and mathematical analysis of central concepts, such as the Auto-Regressive (AR) process generator and Moving Average (MA) identifier are explained in detail. The direct relationship between an adaptive PEF and a digital Proportional-Derivative (PD) controller is also presented. This leads to the development of an adaptive Proportional-Derivative + Integral (PD+I) control structure which is an effective substitute to a conventional PID controller. Experimental validation shows that the approach results in a fast adaptive controller with self-loop compensation. (6 pages)A combined interpolation method for waveform reconstruction in beacon transmitter detector
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0889
When beacon transmitter detector making measurements on high speed beacon signal, interpolation is required to reconstruct waveform from sampled waveform data for optimal waveform viewing. In this paper, the linear interpolation and sine interpolation are introduced and analyzed firstly. Then utilizing the characteristics of beacon transmitter detector, a combined interpolation method which consists of the linear interpolation and sine interpolation is proposed. Simulation results show that the proposed combined method has good waveform reconstruction performance and relatively low computational complexity. It is very suitable for implementation of waveform reconstruction in beacon transmitter detector.Application of wedge functions to 2D magnetostatic problems
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0027
In this paper the application of so called wedge functions is presented to solve two-dimensional simple geometries magnetostatic and electrostatic problems, e.g. rectangles of varying aspect ratio and with different values of the magnetic permeability μ. Such wedge solutions contain surface pole distributions of a certain power. The same pole distribution functions have been used in the analysis of conducting and infinite permeability structures. Here we apply such functions in a boundary integral analysis method of finite permeability.Using Canny algorithm in QEM simplification for textured 3D models
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0900
In this paper, based on edge collapse an improved method of texturing 3D models is promoted, which take the texture into and consideration and make use of Canny algorithm to calculate the borders. We use edge collapse algorithm to simplify the 3D models and the collapse sequence is depended on the collapse cost which combine the edge collapse and the texture collapse. Before simplification, fist using Canny algorithm to calculate the border of the model to keep the basic skeleton of the models.Performance analysis of self-regulated and self-excited six-phase induction generator
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0410
This paper presents a simple method to determine the performance of a Self-regulated, Self-Excited Six-Phase Induction Generator. The problem is formulated as multivariable unconstrained non linear optimization problem. The admittance of the equivalent circuit of the Six-Phase Self-Excited Induction Generator (SPSEIG) is taken as an objective function. Attention is focused on the influence of the different capacitor connections on the generator overload and output power capabilities. The generator voltage with simple shunt excitation connection collapses when it is overloaded. With short shunt excitation connection, the generator is able to sustain the load but at lower operating voltage and larger load current. The frequency and magnetic reactance or speed and magnetic reactance or frequency and capacitive reactance are selected as an independent variables depending upon the operational condition of the machine. The optimization problem is solved using Fmincon method. The developed mathematical model is quite simple and can be implemented for any type of load such as resistive or reactive with capacitor connected either across single three-phase winding set or both the winding sets. The computed results are found to be in good agreement with the experimental results.FE analysis of coupled phenomena in actuators with magnetorheological fluids
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0006
The paper deals with coupled electromagnetic, hydrodynamic, thermal and mechanical motion phenomena in magnetorheological fluid actuators. The governing equations of these phenomena are presented. The numerical implementation of the mathematical model is based on the finite element method and a step-by-step algorithm.Comparison of single-phase cascaded and multilevel DC link inverter with pulse width modulation control methods
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0366
This paper presents comparison of cascaded H-Bridge and multilevel dc link inverter using only a dc power sources. The performance of a seven level multilevel dc link inverter based on sine and space vector pulse width modulation control technique. Performance analysis is made based on the results of simulation study conducted on the operation of the multilevel dc link inverter using MATLAB/SIMULINK. The performance parameters chosen in the work include the waveform pattern harmonic spectrum, fundamental value and total harmonic distortion (THD) of the single phase multilevel dc link inverter.Two-level approach for solving the inverse problem of defect identification in eddy current testing-type NDT
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0071
An inverse problem of 3D crack identification inside a conductive material from the eddy current measurements is investigated. In order to accelerate the time-consuming direct optimization, the reconstruction is provided by the minimization of a last-square functional of the data-model misfit using space mapping (SM) methodology. This technique enables to shift the optimization load from a time consuming and accurate model to the less precise but faster coarse surrogate. In this work, the finite element method (FEM) is used as a fine model, while the model based on the volume integral method (VIM) serves as a coarse model. The application of this method to the shape reconstruction allows to shorten the evaluation time that is required to provide the proper parameter estimation of surface defects.Effect of fractional-order controller on automatic generation control of a multi-area thermal system
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0365
A concept of fractional order (FO) control has received an increasing interest recently in the control areas. This paper investigates the effect of a fractional-order Proportional plus Integral plus Derivative (FOPID) controller in automatic generation control (AGC) of interconnected two unequal and three unequal area thermal systems considering appropriate generation rate constraint (GRC). Integral square error (ISE) criteria have been used as performance index to design the optimal controller keeping frequency bias setting fixed at frequency response characteristics. The performance of FOPID controller is investigated and compared with several integer-order (10) classical controllers such as integral (I), Proportional plus Integral (PI), Proportional plus Integral plus Derivative (PID). The optimum value for several parameters is obtained using classical approach minimising cost function J. Studies reveal that FOPID controller having five tuning knobs are quite robust and provide superior dynamic performances in terms of settling time and reduction in oscillation of frequency and tie line power deviation dynamic response as compared to all the conventional 10 controllers. System performances are examined with 1% step load perturbation in ureal.On an inverse electromagnetic procedure for frequency and spatial reconstruction of the lightning return stroke current
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0054
An inverse problem is proposed for the identification of the lightning return stroke current, from the electro magnetic fields that occur. The approach deals with Fredholm integral equations of the first kind and with an improved regularization procedure based on a spatial and time dependent harmonic reconstruction of the lightning current. All the preliminary evaluations appear to be in good agreement with the actual characterization current models for the lightning; moreover the precision as regarded to the effect is considerably improved.Analysis, design and testing of a novel direct-drive wave energy converter system
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0122
A coupled electromechanical and hydrodynamic simulation of a direct-drive generator connected to a heaving buoy for wave energy conversion has been developed. The system is based around a novel linear generator referred to as 'Snapper" which incorporates a magnetic coupling, resulting in a latching power take-off mechanism. The system has been simulated in the time domain using the Matlab differential equation solvers, and a prototype generator designed, built and tested. (6 pages)Optimum power flow control algorithm for an ultracapacitor bidirectional DC-DC converter
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0158
In this paper, new modulation schemes are proposed to minimise the circulating power flow, minimise RMS currents and maximise the operating efficiency of a voltage-fed phase-shifted bidirectional DC-DC converter for an ultracapacitor energy buffer, with an IGBT voltage doubler circuit. The mathematical analysis to obtain an optimum power flow controller of the bidirectional converter is presented. Theoretical and simulation results show that the proposed method can maintain minimum circulating power flow even if the ultracapacitor voltage is fluctuating between 50% and 100% of the rated voltage. Furthermore, using the proposed modulation methods a considerable improvement in converter efficiency (up to 93.4%) is achieved in comparison to that for the conventional phase-shift modulation method (around 80%). The proposed modulation scheme is verified by PSpice/Simulink co-simulation using SLPS. (7 pages)Optimal balancing of large single-phase traction load
http://dl-live.theiet.org/content/conferences/10.1049/ic.2010.0017
Traction load results in voltage unbalance. Steinmetz method for balancing traction load has disadvantage required high compensation capacity. This paper presents a model with optimal compensation capacity for balancing traction load. According to the mathematical analytic solution of the optimal model, comparisons between the optimal results and that of Steinmetz method are conducted with MATLAB, which demonstrates the advantages of the optimal design. (6 pages)Audio-visual convolutive blind source separation
http://dl-live.theiet.org/content/conferences/10.1049/ic.2010.0225
We present a novel method for speech separation from their audio mixtures using the audio-visual coherence. It consists of two stages: in the off-line training process, we use the Gaussian mixture model to characterise statistically the audio- visual coherence with features obtained from the training set; at the separation stage, likelihood maximization is performed on the independent component analysis (ICA)-separated spectral components. To address the permutation and scaling indeterminacies of the frequency-domain blind source separation (BSS), a new sorting and rescaling scheme using the bimodal coherence is proposed. We tested our algorithm on the XM2VTS database, and the results show that our algorithm can address the permutation problem with high accuracy, and mitigate the scaling problem effectively. (5 pages)Rail modelling for large-scale railway network frequency analysis
http://dl-live.theiet.org/content/conferences/10.1049/ic.2010.0032
A new state of the art frequency analysis tool (FAPS) for modelling electric traction systems has been developed by TNEI as a joint development with Alstom Transport and SNCF. The objective is to significantly improve the harmonic modelling and frequency domain characterisation of electric rail networks. The sufficiently accurate modelling of both passive and active components is key to the creation of a practical system simulation tool and a number of simplification assumptions about the electromagnetic behaviour of rails are necessary in order to provide a practical tool for large system analysis. A high-resolution finite element (FE) analysis was carried out to evaluate the validity and applicability of these assumptions as part of this development process. (5 pages)Analytical analysis of PT ferroresonance in the transient-state
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.0260
Potential transformer (PT) ferroresonance might happen due to a capacitance when a circuit breaker is opened. In this case, the iron core repeats saturation and unsaturation. This paper describes an analytical analysis of PT ferroresonance in the transient-state. In this paper, the iron core is modelled by simplified two-segment core model to analyze ferroresonance analytically. Thus, a nonlinear ordinary differential equation (ODE) for the flux linkage is changed into a linear ODE with constant coefficients, which enables an analytical analysis. In this simplified model, each state, which is either saturated or unsaturated state, corresponds to one of the three modes, i.e. overdamping, critical damping and underdamping. The flux linkage and the voltage in each state are obtained analytically by solving the linear ODE with constant coefficients. The proposed transient analysis seems simple but effective in the more understanding of ferroresonance and thus can be used to design a ferroresonance suppression circuit of a PT. (5 pages)On the use of time-frequency distributions for the power quality problem of harmonics
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.0865
The presence of harmonics in the electric voltage or current waveforms constitutes a steady-state type of Power Quality event Harmonics are sinusoidal components at frequencies that are integer multiples of the fundamental frequency (50 Hz or 60 Hz, in the electric power systems). These are produced by the non-linear characteristics of the devices and loads, causing Power Quality disturbances. In this work signal processing methods are developed or appropriately adapted in order to detect harmonics and to estimate their frequency and power relative to that of the fundamental frequency. A practical problem is that neither are harmonics continuously present in the waveforms nor is their relative powers constant. For the spectral analysis of signals whose statistical properties vary in time (non-stationary signals), time-frequency distribution methods, rather than Fourier analysis based methods, are pertinent. Indeed, time-frequency distributions allow us to observe the evolution of the signal frequency content in time. The most popular time-frequency distribution is the Fourier magnitude spectrogram (squared magnitude of the Short-Time Fourier Transform, STFT). However, for applications such as signal variations detection, where increased time and frequency resolutions are required, the Choi-Willians Distribution (CWD), a member of the Cohen-class distributions family, is preferable. Its efficiency for harmonics detection and estimation is shown here by simulations on synthetic signals with satisfactory results. (5 pages)An adaptive window switching method for ITU-T G.719 transient coding in TDA domain
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.0675
The paper proposes an adaptive window switching method based on Time Domain Aliasing (TDA) signal to improve the performance of ITU-T G.719 transient audio coding. As to the transient frame, the TDA output signal is analyzed with variable window length to obtain optimal time-frequency resolution. An optimal window switching mode is selected by means of open-loop transient position marking and closed-loop mode selection. Experiment results show that the proposed method can reduce the pre-echo artifacts of G.719 transient coding while maintain better time-frequency analysis effect than the fixed window switching method.Towards a method to determine the glottal formant parameters of voiced speech without time-domain references
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.0494
This paper presents an approach to estimate the glottal formant parameters of the voicing source in the frequency-domain. The method is based on a simplified pole-zero interpretation of the prevalent Liljencrants-Fant (LF) model of glottal flow, and gives approximations for a broad range of pulses shapes. An advantage of the method is that, unlike other methods, it does not rely on time-domain references.Research on image filtering method to combine mathematics morphology with adaptive median filter
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.1152
As a imaging technology of no-traditional lamp-house irradiation ,ultrasound medical imaging with its many advantages, such as no harm to the human body, real-time, cheap and easy to use, is widely used in clinic. But the ultrasonic imaging speckle noise make it difficulties to distinguish between normal tissue and pathological tissue. According to the character of noise in the medical ultrasonic image , an new method of the medical ultrasonic imaging filter based on mathematics morphology and adaptive filtering is proposed after analysis of speckle noise and general filter, and an experiment is made to validate. The experimental method is as follows : Firstly the Rayleigh noise is imposed on the original image , and then the median filter and the adaptive median filter are used on the contaminated image. Secondly the morphological filter is used to improve image quality and enhance the contrast , after the adaptive median filter is used on the image, to retain more necessary details. Finally the three noise filtering methods are compared from the images denoise and evaluation . And the results indicate that the new method is superior to other ones.Investigating the effects of repetitive transients on paper insulation
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.0338
Repetitive transient aging is not a well understood phenomena in the high voltage world. For this reason, an aging waveform has been designed to understand what the scale of the impact of these pulses is on the paper insulation of a transformer. The times to breakdown between AC plus transients and clean AC are analysed and a clear trend is identified showing that transients are damaging to the insulation. The experimental method is will be described in detailed and also how these transients are achieved using a simple MOSFET and high frequency transformer. (5 pages)Photonic crystal three wavelength division multiplexing based on multimode interference theory
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.1234
This paper presents a two-dimension photonic crystal triplexer wavelength division multiplexing based on multimode interference theory with 131 μm, l.49μm, and 1-55 μm. According to self-imaging multimode interference effect, the guided modes transmitted in multimode waveguides have different phase shifts due to different propagation constants and thus have different space output fields. When intrinsic mode dispersion curves intersect at one point, the Interference is disappeared at this wavelength. Energy is restricted in the original incident waveguide. This paper realizes three wavelengths division by two cascades. The insertion loss, extinction ratios, and power distribution have been demonstrated by the plane wave expansion method and finite different time domain method. Performance parameters are optimized through structural improvement. This device is not subject to electromagnetic interference and has a small size easy to integrate.Comparison of return-to-zero and non-return-to-zero coded pulses for BOTDA
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.1146
The limitation of long distance sensing (>20 km) based on BOTDA (Brillouin optical time doman analysis) with centimetre spatial resolution, and high strain or temperature resolution include 1) gain saturation of the Stokes signal; 2) pump depletion induced the Brillouin spectrum distortion. The coded pulse offers the best solution to reduce above limiting factors and to improve the signal to noise ratio (SNR). In this paper, two most commonly used pulse formats: non-return-to-zero (NRZ) and return-to-zero (RZ) are used for BOTDA, and it is found that RZ coded pulses offer minimum distortion in the time domain waveform and the Brillouin spectra while NRZ coded pulses introduce spatial broadening which has reduced spatial resolution. For SMF gain saturation occurs at much shorter length (<20 km with 20 ns coded pulses) due to one peak Brillouin spectrum, while for 50 km LEAF fibre with 20 ns coded pulse, no gain saturation is observed due to three Brillouin peaks occurring and we have seen the lower and more uniform Brillouin gain across the fibre length. Using RZ coded pulses of differential Brillouin gain to realize DPP-BOTDA, we achieved 50 cm spatial resolution with the strain resolution of 12 μɛ.Location algorithm for multi-disturbances in fiber-optic distributed disturbance sensor using a Mach-Zehnder interferometer
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.1163
Fiber-optic distributed disturbance sensor (FDDS) can locate a single-disturbance effecting on sensing optical fiber cable, while simultaneous multi-disturbances is possible in the practical applications. The multi-disturbances location algorithm based on correlation theory and frequency-domain analysis for Mach-Zehnder interferometer (MZI) based FDDS is proposed and demonstrated. The theory analysis indicated that the proposed algorithm can locate the multi-disturbances. The difficulty of the proposed method is also discussed, and the future work is presented.Spatial-temporal wave mixing based on planar optical interconnection systems
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.1243
A nonlinear optical processor that is capable of true real-time conversion of spatial-domain images to ultrafast time-domain optical waveforms based on planar optics is designed and simulated in this paper. The combine of femtosecond pulse shaping with planar optical configuration builds a totally new compact and reliable structure. We analyze the theory of this apparatus and consider the design of the particular lens for femtosecond pulse shaping based on planar optics and give the result of simulated with Dammann grating.Modelling of distribution network cell based on grey-box approach
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.0852
The paper presents the modeling of Distributed Network Cell (DNC) based on grey-box approach. The equivalent model of DNC comprises of a converter-connected generator and a composite load model in parallel. The detail development of the equivalent model is described in this paper. The grey-box approach is chosen based on the fact that it offers possibility to incorporate some prior knowledge about DNC structure into model development, make developed model more physically relevant and intuitive compared to black box model and potentially improve the accuracy of the model. The dynamic equivalent model is presented in the form of sixth-order nonlinear state space format and developed from the algebraic and differential equations describing assumed typical components of DNC. (6 pages)Performance analysis of eXplicit Control Protocol (XCP)
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.0613
Mathematical analysis of current congestion control algorithms reveals that, as the delay-bandwidth product (BDP) increases, TCP becomes more oscillatory and prone to instability, regardless of the queuing scheme. To address this problem, a novel approach to Internet congestion control is developed recently. This new explicit Control Protocol (XCP) delivers the highest possible application performance over a broad range of network infrastructure, including extremely high speed and very high delay links that are not well served by TCP. We analyze the performance of XCP and make comparation with TCP. Extensive simulations show that XCP achieves fair bandwidth allocation, high utilization, small standing queue size, and near-zero packet drops, with both steady and highly varying traffic. In this paper, we investigate the XCP in deep sight; also present a simple network in which XCP is locally stable but globally unstable in the presence of latency. The simulation results verify that XCP remains fairness, high utilization for future high bandwidth-delay product network.Synthesizing power electronic switching waveforms for reduced EMI generation
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.0176
A method of analysing switching waveforms using their derivative terms shows that imposing an 'S-shaped' profile on the switching transitions offers significant improvements in the control of power loss and radiated EMI in power converters. Numerical modelling to investigate the effects of varying the timing parameters of the waveforms enables switching transients to be shaped to reduce high-frequency spectral content. The resulting synthesized waveforms are used to demonstrate experimentally that total high-frequency power content is reduced without any associated increase in switching time and therefore power loss. (6 pages)Adaptive tools to conduct harmonic analysis using time domain software
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.1012
The non-linear behaviour of HVDC converters causes distorted voltage and current waveforms in the HVAC network to which it is connected. Typically frequency domain software is used for conducting harmonic analysis (penetration and impedance scan studies) and results are displayed as steady-state quantities not taking into account the dynamic behaviour of the system components. A time domain software package is utilized to perform harmonic analysis and consider the dynamic behaviour of the system components. Thus the contribution of this work is the development of adaptive (compact) tools to simplify harmonic analysis procedures for investigating integrated HVAC/HVDC systems using time domain software. Results are generated and it is found that the developed tools are effective for conducting harmonic analysis using time domain software. (5 pages)Experimental validation of a space vector modulation method for a 4-leg matrix converter
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.0146
Most variable speed AC generation systems use back-to-back converters to supply electrical energy, with fixed electrical frequency and voltage, to a stand-alone load or grid. Matrix Converters (MCs) are a good alternative to back-to-back converters because they have several advantages in term of size and weight. Therefore MCs can be advantageously used in any variable speed generation system where high efficiency, reliability, small size and low weight are considered important factors. Possible applications are mobile power supply systems, variable speed diesel generation schemes and wind energy conversion systems. Nevertheless, to interface a MC-based generation system to unbalanced 3φ stand-alone loads, a fourleg MC is required to provide a path for the zero sequence load current. However, the conventional Space Vector Modulation (SVM) algorithm used with 3×3 MCs cannot be applied to a four-leg matrix converter. Therefore, in this paper a SVM algorithm, adequate for the operation of a 3×4 MC is presented. The proposed modulation scheme is mathematically analysed and experimental results, obtained with an experimental prototype, are discussed. (6 pages)HVAC/HVDC strategy for solving power delivery shortages to a localised area of a national grid
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.1011
The industrial and population growth can cause power delivery problems to a localised area of a national grid. One reason for these power shortages is the insufficient current carrying capacity of existing HVAC transmission line supplying the area. Parallel HVAC line, a HVDC line or combinations of HVAC-HVDC lines are three possible solutions to improve power delivery. This paper investigates the various line possibilities using a cutting edge time domain software tool. The contribution of this work is the development of a strategy (flowchart) involving individual or combinations of HVAC and/or HVDC transmission lines taking into account important decision making factors. Simulation based case studies are conducted as part of the strategy and the results are verified. These results together with the decision making factors are then used to demonstrate that an integrated HVAC-HVDC system could be the chosen solution. The developed strategy is shown to be an effective planning tool. (5 pages)Imaging reconstruction for light scattering from a tenuous random medium
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1714
We consider the basis for describing strong scattering in terms of diffusive processes based on the diffusion equation. Intermediate strength scattering is then considered in terms of a fractional diffusion equation which is studied using results from fractional calculus. This approach is justified in terms of the generalization of a random walk model with no statistical bias in the phase to a random walk that has a phase bias and is thus, only 'partially' or 'fractionally' diffusive. A Green's function solution to the fractional diffusion equation is studied and a result derived that provides a model for an incoherent image generated by light scattering from a tenuous random medium. Applications include image enhancement of star fields and other cosmological bodies imaged through interstellar dust clouds. An example of this application is given. (6 pages)Parabolic wave equation for radio propagation over PEC surface and calm sea surface
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1372
The parabolic wave equation could predict long-range radar coverage within different environment. The wide-angle parabolic equation (WAPE) is presented in this paper, and the initial field of the parabolic equation is calculated through Green function which has a better stability and accurateness. The results of the parabolic equation (PE) have been compared with Two Ray model both above the PEC surface and the sea surface conditions, and all the results are well agreed.Signal simulation and research of PMMW radiometer
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.0186
The conventional simulation of target detection of PMMW (passive millimeter wave) radiometer assumes that the detector only has vertical movement. In this paper, based on the mathematical model of target signal of MMW radiometer, we derive the expression of the antenna temperature in the case that the beam centre is not on the axis, and the detector has horizontal and vertical motion. Simulation results are given, and signal characteristics are analyzed. (4 pages)Performance evaluation of a 16-PSK trellis-coded DS-CDMA system utilized for a satellite to airplane/train link
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1235
The symbol-to-symbol error performance evaluation of a 16-PSK A/DS-CDMA coded satellite-to-airplane/train data link is treated, motivated by recent DVB-S2 similar communication experimentations by the TDP#5 payload onboard the AlphaSat platform. A Fourier-Bessel series based analysis utilizing the characteristic function (CF) expression of the overall disturbance vector is employed to model the simultaneous presence of strong fading and impulsive noise disturbances and strong Doppler frequency shifts. Obtained in quasi-real time simulation results show that the involvement of the trellis codes being constructed over the spreading sequences set leads into significant improvement of the performance of the mobile-to-satellite link. In addition, the presented analysis approach appears to be an attractive solution for concurrent payloads design and adaptive communication platforms, such as software radios. (6 pages)Some remarks on the well-posedness of the EMD algorithm
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1726
We identify two major difficulties with the formulation of a rigorous mathematical theory for the Empirical Mode Decomposition (EMD): a) the concept of the envelope is not well defined, and b) the output of the EMD fails a very simple consistency criterion. (6 pages)Preconditioned adaptive integral method for the analysis of planar microstrip structures
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1366
Adaptive integral method based on far-field expansion is introduced to speed up the analysis of the planar microstrip structure. The auxiliary basis functions are constructed as superposition of point-like current elements located on rectangular grids which reproduce the same far field as generated from the original basis functions. Then it is able to employ the fast Fourier transform technique to speed up the matrix vector multiplication required by the iterative solver. The resultant linear systems are then preconditioned by the symmetric successive over relaxation technique to further accelerate iteration. Compared to the previous scheme, the proposed algorithm makes a reduction in both the computational complexity and the storage requirement to attain the same precision.Hybrid time-frequency domain of analysis on power quality disturbances
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1823
Power quality disturbance imposes problems to the reliability of electrical distribution system. Traditional method of detecting these disturbances by using Fast Fourier Transformation (FFT) has drawback of limitation for detection of stationary disturbances only. Wavelet Packet Transform (WPT) is commonly used to detect the non-stationary disturbances but the exact frequency content cannot be seen. In this paper, a hybrid time-frequency approach is envisaged to reserve the respective domain information. Simulation results show that the intrinsic problem of FFT and WPT is resolved. (6 pages)Electromagnetic analysis of finite and curved frequency selective surfaces using the VSIE with MLFMA
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1362
In this paper, the hybrid volume-surface integral-equation (VSIE) approach is proposed to analyze the transmission and reflection characteristics of finite and curved frequency-selective surfaces (FSS) structures. The surface current and electric flux density is expanded by surface RWG and volume SWG basis functions, respectively. The multilevel fast multipole algorithm (MLFMA) is applied to reduce the computational complexity. Simulated results are given to demonstrate the accuracy and efficiency of the proposed method.Scattering computation of slightly rough gaussian surfaces by Kirchhoff approach with harmonic extraction analysis
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1324
The problem of electromagnetic wave scattering from rough surfaces has been the subject of intensive investigations over the past several decades for its applications in a number of important remote sensing implementations. For slightly rough surfaces that the radius of curvature of surface is bigger than the wavelength, the Kirchhoff method is the most commonly used approach. In this paper a new way for scattering computation from rough surfaces is introduced. Here Kirchhoff approach is applied for considering the electromagnetic wave interaction with slightly rough Gaussian surfaces. Fourier series of rough Gaussian surface is used for extracting the strong harmonics of the surface. Then by using the Kirchhoff formulation for periodic surfaces, scattering coefficient is computed. It is shown that by strong harmonics extraction of the rough surface, the acceptable results could be attained. This method could be useful in ray tracing. Asphalt surfaces are simulated by this method in millimeter-wave band. The results are also validated with the method of moments.A comparison of wideband beamformers in coherent situations
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.0298
In this paper, we compare the performance of two classes of adaptive beamformers for wideband and coherent signals. It is well known that when the desired signal and interferences are partially or completely correlated, performance of conventional beamformer degrades severely. Therefore, spatial smoothing method and frequency focusing method have been proposed to tackle coherent sources. In this paper, we first discuss a frequency focusing method which is based on time-domain and can be applied to real time systems. And then, a new wideband beamformer was proposed by introducing spatial smoothing method into Frost beamformer. Result of simulations shows that the new beamformer has better frequency response than the time-domain based frequency focusing beamformer. (4 pages)Ensemble and individual noise reduction method for induction-motor signature analysis
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1845
Unlike a fixed-frequency power supply, the voltage supplying an inverter-fed motor is heavily corrupted by noises, which are produced from high-frequency switching leading to noisy stator currents. To extract useful information from stator-current measurements, a theoretically sound and robust denoising method is required. The effective filtering of these noises is difficult with certain frequency-domain techniques, such as Fourier transform or Wavelet analysis, because some noises have frequencies overlapping with those of the actual signals, and some have high noise-to-frequency ratios. In order to analyze the statistical signatures of different types of signals, a certain number is required of the individual signals to be de-noised without sacrificing the individual characteristic and quantity of the signals. An ensemble and individual noised reduction (EINR) method is proposed as the extension of the common averaging method for induction-motor signature analysis. The signals after de-noising by the proposed EINR method will preserve the individual characteristics. A number of signals are selected as an ensemble part in the proposed EINR method and are employed as the "profile" to de-noise other individual signals. The case study presented in this paper demonstrates the merits of the proposed EINR method for induction-motor signature analysis. (6 pages)Musical noise reduction based on spectral subtraction combined with Wiener filtering for speech communication
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.2056
The goal of this paper is to propose a new technique for musical noise reduction used to alleviate some of the speech distortion introduced by the spectral subtraction (SS) process, particularly to eliminate the background musical noise of actual environment in speech communication or recognition system. The new speech enhancement approach combines spectral subtraction and the conventional Wiener filtering (CWF) in series connection to construct a two-stage hybrid system (named SS-CWF) in frequency domain to enhance the speech with additive musical noise. The noisy speech is recorded under the real background musical noise environment at a relatively lower signal-to-noise ratio. Simulation results of the proposed method, comparing with that of the conventional spectral subtraction, show better performance. The performance is evaluated by using the Log Likelihood Ratio (LLR) measure, which is an objective evaluation measure based on linear predictive coding (LPC) techniques. Experiment results have shown that combination SS-CWF method is more robust and efficient. Meanwhile, the subjective evaluation results indicate that this method provides better speech quality with cleaner waveforms and spectrograms in time and frequency domain. Consequently, the proposed technique has complementary advantages of the spectral subtraction and Wiener filter.Joint time-frequency micro-Doppler analysis of electromagnetic backscattering from micro-motion object
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1373
Mechanical vibration or rotation of structures in a target may induce frequency modulation on returned signals and generate side-bands about the center frequency of the target's body Doppler frequency. The modulation due to vibrations, which is usually at very low frequencies relative to the body Doppler frequency, is called micro-Doppler phenomenon. Radar cross section (RCS) of an object is a function of aspect angle and frequency. When the object is rotating or has a rotating structure on it, the electromagnetic (EM) backscattering is subjects to modulations simultaneously in amplitude and phase that result in asymmetric Doppler spectra about the carrier frequency. The characteristics of the spectra are determined by the geometry, dimension, and the rotation rate of the rotating part.TEPCO-BCU for on-line dynamic security assessments of large-scale power systems
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1874
The current direction of development for fast transient stability assessment is to combine a reliable direct method and a fast time-domain method into an integrated methodology to take advantage of the merit of both methods. TEPCO-BCU is developed under this direction by integrating BCU method, BCU classifiers, and BCU-guide time domain method. Current version of TEPCO-BCU is able to perform exact stability assessment and accurate energy margin computation of each contingency of large-scale power systems. Exact stability assessment is meant to classify stable contingencies as stable and unstable contingencies as unstable while accurate energy margin computation is meant to give accurate critical clearing time of each contingency of large-scale power systems. To bypass the difficulty of checking the one-parameter transversality condition of BCU method, the concept of the boundary property has been proposed and a group-based BCU method has been developed. This paper has described on-line transient stability assessment results of TEPCO-BCU program on a 12,000-bus power system data. Feasibility study of applying Parallel TEPCO-BCU to on-line transient stability evaluation in terms of speed and accuracy of stability assessment has been conducted. It has been found that the wall clock time needed to process 3,000 contingencies on the 12,000-bus system is 29.5 minutes, 15.5 minutes and 3.1 minutes respectively on a 1-node, 2-node and 10-node configurations. Given a credible list of contingencies, TEPCO-BCU system can fast screen out critical contingencies. This capability in conjunction with some relevant functions can lead to several practical applications. These relevant functions include the energy function method, the controlling UEP coordinates and their sensitivities with respect to parameters or control actions. (14 pages)